ethical

having to do with ethics or morality; of or conforming to moral standards

conforming to the standards of conduct of a given profession or group

designating or of a drug obtainable only on a doctor's prescription

Origin of ethical

Middle English ethik ( from Classical Latin ethicus from Classical Greek ?thikos from ?thos, character, custom from Indo-European base an unverified form swedh-, essential quality, own character from source Gothic swes, Classical Latin suus, one's own and suescere, to become accustomed) + -al

In general usage ethical is used to describe standards of behavior between individuals, while moral or immoral can describe any behavior. You can call lying unethical or immoral, for example, because it involves the behavior of one person and how it affects another, but violating dietary prohibitions in a holy text can only be described as immoral.